Chapter 12

Types of Chemical Bonds

– bond- a force that holds groups of two or more atoms together and makes them functional as a unit
– bond energy- the energy required to break a bond (if it takes more energy to break the bond, the stronger the bond was)
– Ionic bonds- attraction between a strongly positive ion and a strongly negative ion
– ionic compound- compounds that are formed by ionic bond
– Covalent bond- a bond is form between atoms with electrons are shared by the nuclei
– Problem- what is the result when Metals(+) react with a nonmetal(-)? ionic compound
– bond polarity
– the partial positive and negative charges on the atoms
– depends on the difference between the electronegativity values of the atoms forming the bond
For more information on chemical bonds, go to this website

– bond energy- the energy required to break a bond (if it takes more energy to break the bond, the stronger the bond was)

– Ionic bonds- attraction between a strongly positive ion and a strongly negative ion

– ionic compound- compounds that are formed by ionic bond

– Covalent bond- a bond is form between atoms with electrons are shared by the nuclei

– Problem- what is the result when Metals(+) react with a nonmetal(-)? ionic compound

– bond polarity

– the partial positive and negative charges on the atoms

– depends on the difference between the electronegativity values of the atoms forming the bond

For more information on chemical bonds, go to this website

Electronegativity

– the relative ability of an atom in a molecule to attract shared electrons to itself
– chemists determine the electronegativity values for the elements by measuring the polarities of the bond between various atoms

– chemists determine the electronegativity values for the elements by measuring the polarities of the bond between various atoms

– problem- if the electronegativity difference is zero, what is the bond type? covalent
– problem- if the bond type is polar covalent, what is the range? .01-2
– problem- if a bond ranges greater than 2, what is the bond type? ionic

– problem- if the bond type is polar covalent, what is the range? .01-2

– problem- if a bond ranges greater than 2, what is the bond type? ionic

Determining bond polarity
– Problem- Cl-H? .9 (polar covalent)
– Problem- F-H? 1.9 (polar covalent)
– Problem- H-H? 0 (covalent)
– Problem- What is the order from least polar to most polar? H-H, Cl-H, F-H

– Problem- Cl-H? .9 (polar covalent)

– Problem- F-H? 1.9 (polar covalent)

– Problem- H-H? 0 (covalent)

– Problem- What is the order from least polar to most polar? H-H, Cl-H, F-H

Bond Polarity and Dipole Moments

Dipole moment
– magnitudes of separated charges times the distance between the charges
– any diatomic molecule that has a polar bond has a dipole moment
– some poly atomic molecules also have dipole moments

– magnitudes of separated charges times the distance between the charges

– any diatomic molecule that has a polar bond has a dipole moment

– some poly atomic molecules also have dipole moments

– Problem- does the arrow points towards the positive or negative charge center? negative
– Problem- what does the tail indicate? positive center of charges
For more information, watch this video

– Problem- what does the tail indicate? positive center of charges

For more information, watch this video

Stable Electron Configurations and Charges on Ions

Electron Configurations of Ions
1. Representative metals forms ions by losing enough electrons to achieve the configuration of the previous noble gas.
2. Nonmetals forms ions by gaining enough electron to achieve the configuration of the next noble gas
– in almost all stable chemical compounds of the representative elements, all of the atoms have achieved a noble gas electron configuration
Electron Configurations and Bonding
1. When a nonmetal and a Group 1, 2, or 3 metal react to form a binary ionic compound, the ions form in such a way that the valence electron configuration of the nonmetal is completed to achieve the configuration of the next noble gas, and the valence orbitals of the metal are emptied to achieve the configuration of the previous noble gas. In this way, both ions achieve noble gas electron configurations
2. When two nonmetals react to form a covalent bond, they share electrons in a way that completes the valence electron configurations of both atoms. That is, both nonmetals attain noble gas electron configurations by sharing electrons
Problem- What is the electron configure for Na and Na+?

1. Representative metals forms ions by losing enough electrons to achieve the configuration of the previous noble gas.

2. Nonmetals forms ions by gaining enough electron to achieve the configuration of the next noble gas

– in almost all stable chemical compounds of the representative elements, all of the atoms have achieved a noble gas electron configuration

Electron Configurations and Bonding

1. When a nonmetal and a Group 1, 2, or 3 metal react to form a binary ionic compound, the ions form in such a way that the valence electron configuration of the nonmetal is completed to achieve the configuration of the next noble gas, and the valence orbitals of the metal are emptied to achieve the configuration of the previous noble gas. In this way, both ions achieve noble gas electron configurations

2. When two nonmetals react to form a covalent bond, they share electrons in a way that completes the valence electron configurations of both atoms. That is, both nonmetals attain noble gas electron configurations by sharing electrons

Problem- What is the electron configure for Na and Na+?

For more information on electron configurations, watch this video

Ionic Bonding and Structures of Ionic Compounds

– Ionic compound- tend to forms small crystals
– Crystal lattice- the arrangement of ions in an ionic crystal
– a cation is always smaller than the parent atom, and an anion is always larger than the parent atom
– Problem- If you have a cation Mg2+ how many Cl- do I need to balance out the charges of Mg2+? 2 Cl-
– Problem- ionic compounds at room temperature? solid

– Crystal lattice- the arrangement of ions in an ionic crystal

– a cation is always smaller than the parent atom, and an anion is always larger than the parent atom

– Problem- If you have a cation Mg2+ how many Cl- do I need to balance out the charges of Mg2+? 2 Cl-

– Problem- ionic compounds at room temperature? solid

Lewis Structures

Lewis Structure
– representation of a molecule that shows how the valence electrons are arranged among the atoms in the molecule
– the most important requirement for the formation of a stable compound is that the atoms achieve noble gas electron configurations
1. duet rule- hydrogen forms stable molecules where it shares two electrons

– representation of a molecule that shows how the valence electrons are arranged among the atoms in the molecule

– the most important requirement for the formation of a stable compound is that the atoms achieve noble gas electron configurations

1. duet rule- hydrogen forms stable molecules where it shares two electrons

2. helium does not form bonds because its valence electron orbital is already filled (it is a noble gas)

3. octet rule- elements want to have 8 electron on the outer shell
– bonding pair- when an atom is surrounded by eight valence electrons, two which are shared with other atoms
– lone pairs/unshared pairs- has three pairs of electrons that are not involved in bonding

– bonding pair- when an atom is surrounded by eight valence electrons, two which are shared with other atoms

– lone pairs/unshared pairs- has three pairs of electrons that are not involved in bonding

4. neon does not form bonds because it already has an acted of valence electrons (it is a noble gas)

Writing Lewis structures
1. we must include all the valence electrons from all atoms. The total number of electrons available is the sum of all the valence electrons from all the atoms in the molecule
2. Atoms that are bonded to each other share one or more pairs of electrons
3. The electrons are arranged so that each atom is surrounded by enough electrons to fill the valence orbitals of that atom. This means two electrons for hydrogen and 8 for second nonmetals.

1. we must include all the valence electrons from all atoms. The total number of electrons available is the sum of all the valence electrons from all the atoms in the molecule

2. Atoms that are bonded to each other share one or more pairs of electrons

3. The electrons are arranged so that each atom is surrounded by enough electrons to fill the valence orbitals of that atom. This means two electrons for hydrogen and 8 for second nonmetals.

Lewis Structures of Molecules with Multiple Bonds

– single bond- involves two atoms sharing one electron pair

– double bond- involves two atoms sharing two pairs of electrons

– triple bond- three electron pairs are shared

– resonance- when more than one Lewis structure can be drawn for the molecule

Molecular Structure

– molecular structure (geometric structure) – the three dimensional arrangement of the atoms in the molecule

Problems:
bent?

bent?

linear?

trigonal planar?

tetrahedral?

For more practice on Lewis structures & molecular shapes, play this game

Molecular Structure: The VSEPR Model

valence shell electron pair repulsion model
– useful for predicting the molecular structures of molecules formed from nonmetals
– the structure around a given atom is determined by minimizing repulsions between electron pairs
– whenever two pairs of electrons are present around an atom, they should always be placed at an angle of 180 degrees to each other to give a linear arrangement

– useful for predicting the molecular structures of molecules formed from nonmetals

– the structure around a given atom is determined by minimizing repulsions between electron pairs

– whenever two pairs of electrons are present around an atom, they should always be placed at an angle of 180 degrees to each other to give a linear arrangement

Molecular Structure: Molecules with Double Bonds

– when using the VSEPR model to predict the molecular geometry of a molecule, a double bond is counted the same as a single electron pair
Problem- what is the molecular structure of NO3- using VSEPR model?

Problem- what is the molecular structure of NO3- using VSEPR model?

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